Petroleum vapor recovery system



Aug. 2, 1960 GASOLINE PLAN T WEL L J TPfAM H. S. AUBREY PETROLEUM VAPORRECOVERY SYSTEM Filed April 21, 1958 INVENTOR. Herman 6'. Aubrey UnitedStates Patent 2 ,947,379 PETROLEUM VAPOR RECOVERY SYSTEM Herman S.Aubrey, Tulsa, Okla., assignor, by mesne assignments, to National TankCompany, Tulsa, Okla., a corporation of Nevada Filed Apr. 21, 1958, Ser.No. 730,012

7 Claims. (Cl. 183-2) This invention relates to a method and apparatusfor the recovery of hydrocarbon vapors which evolve from crude petroleumliquid in containers, or tanks.

The products of oil wells often contain a large amount of the lightestgases, such as methane, ethane, propane and some butanes which will notremain in a liquid phase under storage conditions. When these wellproducts are placed in containers, or tanks, for any length of time,these lighter gases boil. In boiling, these lighter fractions ofhydrocarbons drive off a finite quantity of the heavier valuablefractions which could otherwise be stored in a liquid state. It is verydesirable that these heavier fractions of hydrocarbons be returned to aliquid phase, within the container, in order to maintain the gravity ofthe crude petroleum at its maximum value. Further, it is desirable tocompress the lighter fractions so they can be received by a gasolineplant.

A primary object of the present invention is to withdraw vapors whichevolve from crude petroleum and condense and absorb them in a liquid sothey can be returned to the body of crude petroleum as a liquid phase.

Another object is to withdraw both the vapors which evolve from crudepetroleum and a portion of the liquid petroleum which is cooler than thevapors and compress the two phases together, returning the resultingliquid phase to-.the body of crude petroleum to maintain the gravity ofthe body at a maximum, and delivering the compressed vapor phase to agasoline plant.

Another object of the invention is to withdraw vapors which evolve froma container of crude petroleum while maintaining a predetermined rangeof container pressure and returning the vapor to the container as aliquid phase to maintain the gravity of the crude petroleum at itsmaximum value.

The present invention contemplates the incorporation of a liquid sealedcentrifugal displacement type of vapor compressor in a system fordrawing evolved vapors from a container of liquid petroleum. The vaporsare compressed by liquid as a piston. Additionally, the vapors areabsorbed, to a degree, by the cooler liquid piston. The compressedliquid and vapor phases are then separated, the liquid and its absorbedvapors being inserted into the body of liquid petroleum in the containerand the compressed vapors being routed to a point of use, such as agasoline plant.

The invention further contemplates a system for drawing evolvedhydrocarbon vapors and cooler liquid petroleum from a container ofliquid petroleum and compressing the two phases together when thecontainer pressure is within predetermined limits. A separator vesselreceives and divides'the compressed phases. A conduit system is providedto return the liquid petroleum and absorbed vapor to the container tomaintain the gravity of the liquid petroleum at its maximum value and topass the compressed vapor to a point of use, such as a gasoline plant.

The invention further contemplates the petroleum vapor recovery systemincluding a switch responsive to container i the compressor is startedand closed when the compressor is stopped. Further, a valve is providedto insure suflicient sealing liquid petroleum is provided duringstart-up of the system to the compressor. Further, a valve is providedto prevent flooding of the compressor and separator when the system isstopped. Further a valve is arranged to control the by-pass of pressureoutput of the compressor around to the compressor input under thedirection of the input pressure to the compressor to prevent containerpressure being reduced until air is vented into the tank. Fun ther, asystem is provided to introduce vapor from a second source into thecontainer, preventing the container pressure being reduced until air isvented into the tank.

Other objects, advantages and features of this invention will appearfrom a consideration of the drawings together with the writtenspecification and claims.

The single figure of drawings is a somewhat diagrammatic illustration ofa complete system embodying the preferred form of the invention.

Referring to the unit and connections of the drawing, a separator 1 isindicated, receiving a well stream through conduit 2. The liquid phasefrom this separator 1 is indicated as being removed through conduit 3.The vapor phase is removed through conduit 4. The liquid phase ofconduit 3 may require further treatment. The liquid hydrocarbon contentof conduit 3 is ultimately placed within tank 5.

At 6 is shown a valve to atmosphere which will function to vent andadmit air to tank 5 only as a safety precaution. Normally vent 6 will beclosed. However, should the capacity of the repressuring means for thetank 5 be exceeded, the valve 6 can be set to admit air to the tank at apredetermined minimum pressure. Should the capacity of the system fordrawing ofi vapor be exceeded, and pressure build up to a predeterminedmaximum, valve 6 can be also set to open and relieve the excessivepressure to atmosphere.

When tank, or container, 5 has a substantial body of liquid hydrocarbonsplaced therein, many of the lighter fractions boil, or evolve, as vaporsat storable condition. The variation of temperatures over a 24 hourcycle will cause the tank to breathe. Breathing will result inalternately losing valuable hydrocarbon fractions to atmosphere andintroducing air into the tank, increasing fire hazard and corrosionpossibility. The present invention provides a conduit 10 through whichthe evolved vapors are drawn during the period the tank pressure is in apredetermined range. Conduit 11 is also provided, near the bottom oftank 5, to draw oil a portion of the liquid hydrocarbons which arecooler than the vapor. The liquid and vapor phases are brought togetherin a compressor 12 of particular form and function.

In general, compressor 12 is of a form which utilizes the relativelycooler liquid hydrocarbons from conduit 11 as a piston to compress thevapor phase of conduit 10. In compressing the vapors, the liquid absorbsa significant portion of the vapors, efiectively returning them toliquid form. Additionally, the cooler temperature of the liquidhydrocarbon piston causes the compressed vapors evolved from the top oftank 5 to condense to liquid form. The two phases, compressed to apressure higher than that of the tank are taken to a separator 13. Thevapor phase is removed through conduit 14 and the liquid phase isremoved through conduit 15.

The liquid phase, now containing substantially all of the valuable,storable, heavy ends boiled from the liquid of tank 5, is returned tothe bottom of tank 5 atthe higher pressure and temperature intermediatethe vapor tank 5. The temperature of liquid phase of conduit 15 isintermediate that of the vapor at the top of the tank and liquid at thebottom by reason of the heat added by compression in 12. The heavierhydrocarbon fractions, returned to the tank under these conditions of.temperature and pressure, will have a tendency to remain in their liquidstate. I

From the foregoing broad consideration of the operation of the system,the compressor is considered in its particular form and function whichenters into the combination to produce the desirable new result attainedby the invention. Basically, the structure comprises a round rotor withcurved blades 16 forming a series of chambers, open at the bottom, andrevolving freely in an elliptical casing partially filled with liquid.As the rotor revolves it carries the liquid with it, resulting in asolid liquid ring .revolvng in the casing at the same speed as therotor.

Since the casing is elliptical and the'rotor round, the q d must ernatly nter an ll the cham ers etween blades 16, and then leave them, in amntinuous .cycle. At the points where the liquid leaves the rotorchambers it draws in vapor through ports 17 in the center of the rotor,connected with the pump inlet. As the liquid-is forced by the convergingcasing to neenter the rotor chambers the vapor in the chamber is forcedout through ports 18 connected with the pump outlet.

One possible form of motive power for the compressor 12 is illustratedas provided by an electric motor 1; 9,'

reduced to a predetermined lower value, the

permissible to prevent air being vented into the tank. Should switch 20become defective, a regulator as shown 7 in conduit 4 can be provided topermit the flow of vapor from top of separator 1 to maintain t epressure above the minimum value. A primary guard of minimum tankpressure is provided with by-pass conduit 21. Conduit 21 connectsbetween vapor output conduit 14 andyapor inlet conduit 10. A regulatorvalve 22, provided in this conduit 21, is responsive to the tank ,5pressure. As with the regulator in conduit 4, regulator 22 is sensitiveto the tank pressure in order to prevent its value decreasing to whereair is drawn into tank 5. Generally, it appears desirable to set theoperative pressure value of the conduit 4 regulator lower than that ofregulator 22. The circulation rate needed through conduit 21 is fairlylow .to provide'the protection and it is logical to provide it fromconduit 14 which is usually at Ya that carried in separator 1.

'The start-up and shut-down conditions ,of the system are nextconsidered. Valve 25 is located in conduit '11 to control the flow ofliquid hydrocarbons to the compressor 12 as seal fluid. Positioning ofvalve 25 is indicated as established by the control system betweenswitch 2%) and motor '19.

When the complete system is shut down for a period, the pressure builtup by the compressor 12, in separator 13 and in conduit 14, back of thecheck valve 14A, may "be bled ofl through at least the packing glands ofcompressor 12. If this occurs, the head of liquid in tank 5 may causethe liquid to flood the compressor ,and separator. Therefore, valve 25represents one means of preventing flooding. Valve 25 is closed byswitch 20 when motor 19 is stopped and flooding is ,etfectivelyprevented.

pressure lower than ,Also, when the complete system is shut down, animdownstream of compressor 12 into conduit 11. Valve 25 may not closesoon .enough to prevent this pressure driving the liquid back into. tank5. Check valve 26 is provided on the opposite side of valve 25, fromcompressor 12, to prevent this result.

Before start-up, the liquid in compressor 12 may have drained intoseparator 13. The compressor would be quickly damaged by running dry, oreven partially dry, before valve 25 can be opened to pass liquid fromtank 5 to the casing of the compressor. Therefore, it is desirable toprovide a by-pass conduit and valve 27 from between valve 25 and thecompressor to conduit 15. This valve can be automatically opened whenthe system shuts down and automatically energized from the pressureswitch 20, through a time delay relay 27A, to close after a period oftime necessary to assure that valve 25 has opened.

Heretofore, only liquid hydrocarbons have been described for use as theliquid seal-piston of compressor. However, it is to be understood thatit is within the scope of the invention to employ liquids from othersources for this purpose. Any liquid which will function to absorb thehydrocarbon vapor of conduit 10, condense unabsorbed vapor and compressthe remains of the vapor and which can be introduced into the liquid .oftank 5 will carryout the objects of the invention. Further, it isconceivable that a separate pressure source may be provided to bring theliquid to the compressor. The preferred embodiment illustrated uses theliquid hydrocarbons of tank 5, with its head, because of their readyavailability.

From the foregoing it will be seen that this invention is one welladapted to attain all of the ends and objects hereinabove set forth,together with other advantages which are obvious and which are inherentto the apparatus.

It will be understood that certain features and sub- .combinations areof utility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of theclaims.

As many possible embodiments may be made of the invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. A vapor recoverysystem for containers of liquid hydrocarbons including,

a container for the liquid hydrocarbons,

a first conduit for drawing evolved vapors liquid hydrocarbons,

a second conduit for drawing a portion .of the hydrocarbons from thecontainer,

a compressor powered by a motive means and utilizing the liquid as apiston to compress a portion of the evolved vapors to a pressure higherthan that of the container and absorb a portion of the vapors,

a valve in the second conduit which is actuated when the motive means isactuated to open the second conduit When the motive means starts andclose the second conduit when the motive means stops,

and means for separating vthewliquid and the vapor and returning theliquid and absorbed vaporsto the container.

2. A process for recovering hydrocarbon vapors evolved from liquidhydrocarbons, which includes,

collecting .vapors from the liquid hydrocarbons,

withdrawing a portion of the liquid hydrocarbons which are cooler thanthe vapors, 1

utilizing the portion of the cooler liquid hydrocarbons from the liquidto simultaneously condense a first portion of the vapor and absorb asecond portion of the vapor and compress a third portion of the vapor, Ireturning the compressed third portion of the vapor to the collectedvapors from the liquid hydrocarbons when the pressure of the collectedvapors falls below a predetermined minimum value,

separating the liquid hydrocarbon and absorbed vapor from the compressedvapor,

and returning the liquid hydrocarbon and absorbed vapor to the liquidhydrocarbons from which the-vapors evolved.

3. A vapor recovery system for containers of liquid hydrocarbonsincluding,

a container for the liquid hydrocarbons,

a first conduit for drawing evolved vapors from the liquid hydrocarbons,

a second conduit for drawing 'a portion of the liquid hydrocarbons fromthe container,

a compressor powered by a motive means and utilizing the liquid as apiston to compress a portion of the evolved vapors to a pressure higherthan that of the container and absorb a portion of the vapors,

a third conduit between the discharge side of the compressor and theintake side,

a normally closed pressure regulator valve in the third conduitresponsive to pressure on the inlet side of the compressor to open thethird conduit when the inlet pressure falls below a predeterminedminimum value.

and means for separating the liquid and the vapor at the elevatedpressure and returning the liquid to the container.

4. A process for recovering hydrocarbon vapors evolved from liquidhydrocarbons, which includes,

collecting vapors from the liquid hydrocarbons,

withdrawing a portion of the liquid hydrocarbons which are cooler thanthe vapors,

utilizing the portion of the cooler liquid hydrocarbons tosimultaneously condense a first portion of the vapor and absorb a secondportion of the vapor and compress a third portion of the vapor,

returning the compressed third portion of the vapor to the collectedvapors from the liquid hydrocarbons when the pressure of the collectedvapors falls belows a predetermined minimum value,

- adding vapor to the collected vapors from the liquid hydrocarbons whenthe pressure of the collected vapors falls to a predetermined valuebelow the predetermined minimum value,

separating the liquid hydrocarbon and absorbed vapor from the compressedvapor,

and returning the liquid hydrocarbon and absorbed vapor to the liquidhydrocarbons from which the vapors evolved.

5. A vapor recovery system for containers of liquid hydrocarbonsincluding,

a container for the liquid hydrocarbons,

a first conduit for drawing evolved vapors from the liquid hydrocarbons,

a second conduit for drawing a portion of the liquid hydrocarbons fromthe container,

a compressor powered by a motive means and utilizing the liquid as apiston to compress a portion of the evolved vapors to a pressure higherthan that of the container and absorb a portion of the vapors,

a third conduit between the discharge side of the compressor and theintake side,

a normally closed pressure regulator valve in the third conduitresponsive to pressure on the inlet side of the compressor to open thethird conduit when the inlet pressure falls below a predeterminedminimum value,

means for repressuring the container with vapor when the vapor pressurefalls to a predetermined value below the predetermined minimum value atwhich the regulator valve in the third conduit opens the third conduit,

and means for separating the liquid and the vapor at the elevatedpressure and reutnring the liquid to the container.

6. A process for recovering hydrocarbon vapors evolved from liquidhydrocarbons, which includes,

collecting vapors from the liquid hydrocarbons,

withdrawing a portion of the liquid hydrocarbons which are cooler thanthe vapors,

utilizing the portion of the cooler liquid hydrocarbons tosimultaneously condense a first portion of the vapor and absorb a secondportion of the vapor and compress a third portion of the vapor,

circulating cooler liquid hydrocarbons of the portion utilized tosimultaneously condense and absorb and compress the vapor through thecondensing and absorbing and compressing process for an initial periodduring startup of the recovery process,

separating the liquid hydrocarbon and absorb vapor from the compressedVapor,

and returning the liquid hydrocarbon and absorbed vapor to the liquidhydrocarbons from which the vapors evolved.

7. A vapor recovery system for containers of liquid hydrocarbonsincluding, i

a container for the liquid hydrocarbons,

a first conduit for drawingevolved vapors from the liquid hydrocarbons,

a second conduit for drawing a portion of the liquid hydrocarbons fromthe container.

a compressor powered by a motive means and utilizing the liquid as apiston to compress a portion of the evolved vapors to a pressure higherthan that of the container and absorb a portion of the vapors,

"a means for separating the liquid and the vapor at the elevatedpressure and retaining the liquid to the container,

and-a by-pass connection between the compressor intake and theseparating means which is opened to circulate liquid from the separatorthrough the compressor for an initial period during start-up of thesystem.

References Cited in the file of this patent UNITED STATES PATENTS1,653,387 Brown Dec. 20, 1927 1,991,548 De Motte Feb. 19, 1935 2,013,167Musto Sept. 3, 1935 2,126,367 Clawson et al. Aug. 9, 1938 2,765,045Meyers Oct. 2, 1956 2,788,745 Jennings Apr. 6, 1957

2. A PROCESS FOR RECOVERING HYDROCARBON VAPORS EVOLVED FROM LIQUIDHYDROCARBONS, WHICH INCLUDES, COLLECTING VAPORS FROM THE LIQUIDHYDROCARBONS, WITHDRAWING A PORTION OF THE LIQUID HYDORCARBONS WHICH ARECOOLER THAN THE VAPORS, UTILIZING THE PORTION OF THE COOLER LIQUIDHYDROCARBONS TO SIMULTANEOUSLY CONDENSE A FIRST PORTION OF THE VAPOR ANDABSORB A SECOND PORTION OF THE VAPOR AND COMPRESS A THIRD PORTION OF THEVAPOR, RETURNING THE COMPRESSED THIRD PORTION OF THE VAPOR TO THECOLLECTED VAPORS FROM THE LIQUID HYDROCARBONS WHEN THE PRESSURE OF THECOLLECTED VAPORS FALLS BELOW A PREDETERMINE MINUM VALUE, SEPARATING THELIQUID HYDROCARBON AND ABSORBED VAPOR FROM THE COMPRESSED VAPOR,